1. Field of the Invention
The present invention relates generally to an air jet loom and, more particularly, to an automatic picking regulating method for automatically setting and regulating the respective jetting timing of groups of auxiliary nozzles arranged along the picking path of an air jet loom, and an apparatus for carrying out the same.
2. Description of the Prior Art:
Japanese Patent Publication No. 48-31949 (U.S. Pat. No. 3,705,608) discloses an invention relating to a picking means for an air jet loom, in which auxiliary nozzles arranged along the picking path of an air jet loom are activated sequentially with respect to the picking direction in picking a weft yarn by jetting air by a main nozzles. The auxiliary nozzle are activated sequentially in optimum timing to jet air properly into the picking path so as to urge the weft yarn in the picking direction.
Ordinarily, a weft yarn pulled out from a yarn package is measured and stored, for example, by a drum type weft yarn measuring and storing apparatus, wherein the weft yarn stored on the storage drum of the weft yarn measuring and storing apparatus is released from the storage drum in a timed relationship with the picking operation, and then the weft yarn is picked into the picking path by the main nozzle. As the diameter of the yarn package decreases with the repetition of the picking operation, the resistance against pulling out the weft yarn from the yarn package and the resistance against unwinding the weft yarn from the storage drum vary due to the variation of the curling degree of the weft yarn and the resultant variation of the ballooning behavior of the weft yarn. Consequently, the mode of running of the weft yarn along the picking path varies gradually with the progress of the weaving operation.
Japanese Patent Laid-Open Publication No. 54-106664 discloses an invention relating to a picking means for an air jet loom, in which a plurality of auxiliary nozzles are activated sequentially for jetting air to assist the picked weft yarn for running; and the duration of jetting air by the auxiliary nozzles is extended gradually to cope with the variation of the running mode of the weft yarn with the progress of the picking operation. This means, however, entails the useless consumption of compressed air, and disturbs the air current in the picking path by air jetted by the auxiliary nozzles during an unnecessary period, which makes a stable picking operation impossible.
The jet start timing and jet end timing of each group of auxiliary nozzles are determined experimentally by finding the phase angle of the main shaft of the loom corresponding to the moment of arrival of the free end of a weft yarn picked by the main nozzle at the first auxiliary nozzle of the group through the stroboscopic observation of the picked weft yarn and taking the response speed of the picking fluid control valve into account. However, the observation of the free end of the running weft yarn through intervals between the warp yarns is difficult and requires much time, and the accuracy of the result of the observation is unsatisfactory because of variations of the running speed of the picked weft yarn between picking cycles. Furthermore, the recent trend of weaving a variety of fabrics in a small amount on a loom requires frequent changes of the settings of the loom requiring complicated observations for every change of the setting of the loom, which makes optimum jet timing of the auxiliary nozzles difficult. The optimum jet timing of the auxiliary nozzles is important for saving energy as well as for the stable operation of the loom.
U.S. Pat. No. 4,595,039 discloses an invention relating to means for sequentially controlling the jet condition of groups of auxiliary nozzles on the basis of the actual running speed of a picked weft yarn. According to this known invention, the running speed of the picked weft yarn is measured at a position on the arriving side on an assumption that the picked weft yarn runs along a straight path. Therefore, such a means is effective only when the picked weft yarn runs straight through the shed of the warp yarn; however, the picked weft yarn runs rarely along a straight path in an actual weaving operation.